TPO8托福阅读Passage2 Extinction of the Dinosaurs文本+题目原文+答案解析

Extinction of the Dinosaurs

Paleontologists have argued for a long time that the demise of the dinosaurs was caused by climatic alterations associated with slow changes in the positions of continents and seas resulting from plate tectonics. Off and on throughout the Cretaceous (the last period of the Mesozoic era, during which dinosaurs flourished), large shallow seas covered extensive areas of the continents. Data from diverse sources, including geochemical evidence preserved in seafloor sediments, indicate that the Late Cretaceous climate was milder than today’s. The days were not too hot, nor the nights too cold. The summers were not too warm, nor the winters too frigid. The shallow seas on the continents probably buffered the temperature of the nearby air, keeping it relatively constant.

At the end of the Cretaceous, the geological record shows that these seaways retreated from the continents back into the major ocean basins. No one knows why. Over a period of about 100,000 years, while the seas pulled back, climates around the world became dramatically more extreme: warmer days, cooler nights; hotter summers, colder winters. Perhaps dinosaurs could not tolerate these extreme temperature changes and became extinct.

If true, though, why did cold-blooded animals such as snakes, lizards, turtles, and crocodiles survive the freezing winters and torrid summers? These animals are at the mercy of the climate to maintain a livable body temperature. It’s hard to understand why they would not be affected, whereas dinosaurs were left too crippled to cope, especially if, as some scientists believe, dinosaurs were warm-blooded. Critics also point out that the shallow seaways had retreated from and advanced on the continents numerous times during the Mesozoic, so why did the dinosaurs survive the climatic changes associated with the earlier fluctuations but not with this one? Although initially appealing, the hypothesis of a simple climatic change related to sea levels is insufficient to explain all the data.

Dissatisfaction with conventional explanations for dinosaur extinctions led to a surprising observation that, in turn, has suggested a new hypothesis. Many plants and animals disappear abruptly from the fossil record as one moves from layers of rock documenting the end of the Cretaceous up into rocks representing the beginning of the Cenozoic (the era after the Mesozoic). Between the last layer of Cretaceous rock and the first layer of Cenozoic rock, there is often a thin layer of clay. Scientists felt that they could get an idea of how long the extinctions took by determining how long it took to deposit this one centimeter of clay and they thought they could determine the time it took to deposit the clay by determining the amount of the element iridium (Ir) it contained.

Ir has not been common at Earth’s since the very beginning of the planet’s history. Because it usually exists in a metallic state, it was preferentially incorporated in Earth’s core as the planet cooled and consolidated. Ir is found in high concentrations in some meteorites, in which the solar system’s original chemical composition is preserved. Even today, microscopic meteorites continually bombard Earth, falling on both land and sea. By measuring how many of these meteorites fall to Earth over a given period of time, scientists can estimate how long it might have taken to deposit the observed amount of Ir in the boundary clay. [■]  These calculations suggest that a period of about one million years would have been required.  [■] However, other reliable evidence suggests that the deposition of the boundary clay could not have taken one million years. [■]  So the unusually high concentration of Ir seems to require a special explanation. [■] 

In view of these facts, scientists hypothesized that a single large asteroid, about 10 to 15 kilometers across, collided with Earth, and the resulting fallout created the boundary clay. Their calculations show that the impact kicked up a dust cloud that cut off sunlight for several months, inhibiting photosynthesis in plants; decreased surface temperatures on continents to below freezing; caused extreme episodes of acid rain; and significantly raised long-term global temperatures through the greenhouse effect. This disruption of food chain and climate would have eradicated the dinosaurs and other organisms in less than fifty years.

TPO8托福阅读Passage2Extinction of the Dinosaurs题目

Question 1 of 14：According to paragraph 1, which of the following is true of the Late Cretaceous climate?

A. Summers were very warm and winters were very cold.

B. Shallow seas on the continents caused frequent temperature changes.

C. The climate was very similar to today’s climate.

D. The climate did not change dramatically from season to season.

Question 2 of 14：Which of the following reasons is suggested in paragraph 2 for the extinction of the dinosaurs?

A. Changes in the lengths of the days and nights during the late Cretaceous period

B. Droughts caused by the movement of seaways back into the oceans

C. The change from mild to severe climates during the Late Cretaceous period

D. An extreme decrease in the average yearly temperature over 10,ooo years

Question 3 of 14：Why does the author mention the survival of “snakes, lizards, turtles, and crocodiles ” in paragraph 3?

A. To argue that dinosaurs may have become extinct because they were not cold-blooded animals

B. To question the adequacy of the hypothesis that climatic change related to sea levels caused the extinction of the dinosaurs

C. To present examples of animals that could maintain a livable body temperature more easily than dinosaurs

D. To support a hypothesis that these animals were not as sensitive to climate changes in the Cretaceous period as they are today

Question 4 of 14: The word “cope ” in the passage is closest in meaning to

A. adapt

B. move

C. continue

D. compete

Question 5 of 14: According to paragraph 3, which of the following is true of changes in climate before the Cretaceous period and the effect of these changes on dinosaurs?

A. Climate changes associated with the movement of seaways before the Cretaceous period did not cause dinosaurs to become extinct.

B. Changes in climate before the Cretaceous period caused severe fluctuations in sea level, resulting in the extinction of the dinosaurs.

C. Frequent changes in climate before the Cretaceous period made dinosaurs better able to maintain a livable body temperature.

D. Before the Cretaceous period there were few changes in climate, and dinosaurs flourished.

Question 6 of 14: The word “fluctuations ” in the passage is closest in meaning to

A. extremes

B. retreats

C. periods

D. variations

Question 7 of 14: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? In correct choices change the meaning in important ways or leave out essential information.

A. The fossil record suggests that there was an abrupt extinction of many plants and animals at the end of the Mesozoic era.

B. Few fossils of the Mesozoic era have survived in the rocks that mark the end of the Cretaceous.

C. Fossils from the Cretaceous period of the Mesozoic up to the beginning of the Cenozoic era have been removed from the layers of rock that surrounded them.

D. Plants and animals from the Mesozoic era were unable to survive in the Cenozoic era.

Question 8 of 14: In paragraph 4, all the following questions are answered EXCEPT:

A. Why is there a layer of clay between the rocks of the Cretaceous and Cenozoic?

B. Why were scientists interested in determining how long it took to deposit the layer of clay at the end of the Cretaceous?

C. What was the effect of the surprising observation scientists made?

D. Why did scientists want more information about the dinosaur extinctions at the end of the Cretaceous?

Question 9 of 14: The word “bombard ” in the passage is closest in meaning to

A. approach

B. strike

C. pass

D. circle

Question 10 of 14：Paragraph 5 implies that a special explanation of Ir in the boundary clay is needed because

A. the Ir in microscopic meteorites reaching Earth during the Cretaceous period would have been incorporated into Earth’s core

B. the Ir in the boundary clay was deposited much more than a million years ago

C. the concentration of Ir in the boundary clay is higher than in microscopic meteorites

D. the amount of Ir in the boundary clay is too great to have come from microscopic meteorites during the time the boundary clay was deposited

Question 11 of 14：The word “disruption ” in the passage is closest in meaning to

A. exhaustion

B. disturbance

C. modification

D. disappearance

Question 12 of 14：Paragraph 6 mentions all of the following effects of the hypothesized asteroid collision EXCEPT

A. a large dust cloud that blocked sunlight

B. an immediate drop in the surface temperatures of the continents

C. an extreme decrease in rainfall on the continents

D. a long-term increase in global temperatures

Question 13 of 14：Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit?

Consequently, the idea that the Ir in the boundary clay came from microscopic meteorites cannot be accepted..

Question 14 of 14：Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. For a long time scientists have argued that the extinction of the dinosaurs was related to climate change.

A.A simple climate change does not explain some important data related to the extinction of the dinosaurs at the end of the Cretaceous.

B.The retreat of the seaways at the end of the Cretaceous has not been fully explained.

C.The abruptness of extinctions at the end of the Cretaceous and the high concentration of Ir found in clay deposited at that time have fueled the development of a new hypothesis.

D.Extreme changes in daily and seasonal climates preceded the retreat of the seas back into the major ocean basins.

E.Some scientists hypothesize that the extinction of the dinosaurs resulted from the effects of an asteroid collision with Earth.

F. Boundary clay layers like the one between the Mesozoic and Cenozoic are used by scientists to determine the rate at which an extinct species declined.

TPO8托福阅读Passage2Extinction of the Dinosaurs解析

Question 1 of 14

正确答案：D

题目解析：以Late Cretaceous climate做关键词定位至倒数第四句： Data from diverse sources, including geochemical evidence preserved in seafloor sediments, indicate that the Late Cretaceous climate was milder than today’s. The days were not too hot, nor the nights too cold. 说比现在更温和，白天不太热，晚上不太冷。所以D是答案。A与倒数第二句矛盾，错;B与最后一句相反，错;C说跟现在similar，跟原文的milder矛盾。

Question 2 of 14

正确答案：C

题目解析：C 以extinction of the dinosaurs做关键词定位至最后一句，原句说不能忍受这些极端温度的恐龙灭绝了，因为有个these，所以网上看一句，说冬天很冷夏天很热，所以C是答案。A和B都没说;D的decrease没说。

Question 3 of 14

正确答案：B

题目解析：B, 先读所在句，说为什么诸如blabla之类的动物能耐得住这种极端气候呢，而且这句一开始就来了个if true，所以应该是作者在质疑上端所提出的结论的正确性，而且最后一句是本段的中心句，说将气候变化的原因归于sea level是不对的，所以答案是B。

Question 4 of 14

正确答案：A

题目解析：cope: 应付。A是适应;B是移动;C是继续;D是竞争。所以A的adapt适应正确。对应原文 ：It’s hard to understand why they would not be affected, whereas dinosaurs were left too crippled to cope, especially if, as some scientists believe, dinosaurs were warm-blooded.原文说很难理解为什么其他动物没被影响，而恐龙特别弱以至于不能怎么样。转折说明恐龙被影响了，所以应该是难易度过之类的意思，所以A和C靠谱，至于为什么不是C，只能靠认识了。

Question 5 of 14

正确答案：A

题目解析：A 以before the Cretaceous period做关键词，但注意原文中与之对应的是倒数第二句的earlier，问为什么恐龙在之前的动荡中生存了下来而这次没有，所以A是答案，说之前的变化没有引起恐龙灭绝。B说反了;C的恐龙better able to maintain原文没说;D的恐龙flourish繁盛没说。

Question 6 of 14

正确答案：D

题目解析：fluctuation: 波动，震荡，变化。A是极端条件;B是撤退;C是周期;D是变化。所以D的variation正确。对应原文：Critics also point out that the shallow seaways had retreated from and advanced on the continents numerous times during the Mesozoic, so why did the dinosaurs survive the climatic changes associated with the earlier fluctuations but not with this one?原句说为什么恐龙熬过了其他的气候变化而这次没能成功熬过来，fluctuation和one都指change;而且之前还说海道从陆上进进退退，这也是变化，所以variation正确;A极端B撤退C周期都不对。

Question 7 of 14

正确答案：A

题目解析：A 原文的结构是blabla的时候plants and animals从化石中突然消失了。A正确;B错，原文没说few fossil;C把非主干部分变成了主干，而且remove也没说;D选项缺了原文里化石这个很重要的信息，错。

Question 8 of 14

正确答案：A

题目解析：A的layer of clay定位至倒数第二句： Between the last layer of Cretaceous rock and the first layer of Cenozoic rock, there is often a thin layer of clay. 但原文只是说有layer，没说为什么有，所以A的问题没得到回答，选; B的how long和deposit 定位至最后一句，正确，不选： Scientists felt that they could get an idea of how long the extinctions took by determining how long it took to deposit this one centimeter of clay and they thought they could determine the time it took to deposit the clay by determining the amount of the element iridium (lr) it contained. C的surprising observation对应第一句和第二句： Dissatisfaction with conventional explanations for dinosaur extinctions led to a surprising observation that, in turn, has suggested a new hypothesis. C直接对应，正确，不选;D也对应第一句，说对传统理论的不满，导致了一个observation和相应的假说，所以D正确，不选。

Question 9 of 14

正确答案：B

题目解析：bombard: 轰击，炮轰，撞击。A是接近;B是击打;C是经过，通过;D是旋转;环形。所以B的strike正确。对应原文：Even today, microscopic meteorites continually bombard Earth, falling on both land and sea.原句说直到今天，那些显微级的小星体还在怎么样地球，落在陆地上和海里。后半句话是对前半句的的补充说明，意思应该一致。既然是falling on，那么A和B都有可能正确。而bomb的意思是轰炸，炸弹，那么正确的就是B了。

Question 10 of 14

正确答案：D

题目解析：D 显然ir和boundary clay都不可以用来定位，用special explanation定位到最后一句，但这句知识重复了题干，而so就告诉你要往前看。倒数第三四句话说：根据一定时期内落入地球陨星的数量可以推断出积累这么多铹需要多长时间，据此推测需要几百万年;而倒数第二句则说：但可靠的证据表明并没有经历这么长的时间。因此可以推测出，如此高含量的铹需要进一步解释，与 D选项对应。

Question 11 of 14

正确答案：B

题目解析：disruption: 打断，干扰。A是枯竭，耗尽;B是干扰，骚乱;C是修改;D是消失。所以B的disturbance正确。对应原文：This disruption of food chain and climate would have eradicated the dinosaurs and other organisms in less than fifty years.原句一开始就一个this，说明与前文有关，前面是一个很长的句子，说一个impact弄出了一大堆dust cloud，这些cloud做了cut off了阳光，阻碍了光合作用，又做了很多blabla事儿。所以一定是不好的词，C的modification改变中性，不对;A用尽和D消失都说食物链没了，但原文没说食物链消失了，而且两个词意思过于相近也不选。

Question 12 of 14

正确答案：C

题目解析：C，EXCEPT题，排除法。A的dust cloud，B的drop in the surface temperatures和D的increase in global temperatures都能定位至第二句，都正确，不选;C的rainfall原文没说，错，选。

Question 13 of 14

正确答案：C

题目解析：三个过渡点，boundary clay，Ir和consequently，根据boundary clay的话A/B/C可能是答案，根据Ir的话C或者D可能是答案，所以初定答案是C。A点之后说需要一百万年，B点之后的句子说没有一百万年，所以B前后的转折过渡紧密，B排除;而且既然没有一百万年，说明前面的理论不成立，所以待插入句中的consequently插入C的时候因果关系成立，所以C是答案。

Question 14 of 14

正确答案：ACE

题目解析：A. C.E a simple选项对应原文第三段最后一句，正确。the retreat选项对应原文第二段第一句，但这句是气候变化原因的一部分，细节，不选。the abruptness选项对应原文第四段第一句，正确。extreme选项原文没说，不选。some选项对应原文第六段第一句，正确。 boundary clay选项原文没说，不选。

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